Manufacture of dithio bisarylamines



Patented Feb. 3, 1948 MANUFACTURE OF DITHIO BIS- ARYLAMINES PhilipTQPaul and Lyndon B. Tewksbury, Jr., Naugatuck, Conn., assignors toUnited States Rubber Company, New York, N. Y., a corporation of NewJersey No Drawing. Application November 1, 1944,

Serial No. 561,493

3 Claims.

This invention relates to improvements in. the manufacture of dithiobis-arylamines, and more particularly 2,2'-dithiobisaniline having theformula This chemical is also known as o,o-diamino di phenyl disulfide.

2,2'-Dithiobisaniline is easily prepared in a crude state by heatinganiline and sulfur at temperatures ranging between about 1'70 and about180 C. for approximately 20 to 24; hours. A reaction proceeds accordingto the equation NHz At the same time a quantity of 4,4'-dithiobisanilineis formed At the end of this heating period the reaction mixtureconsists of 2,2'-dithiobisaniline, 4,4- dithiobisaniline and a largequantity of unreacted aniline and sulfur.

While the unreacted aniline can be separated readily by vacuumdistillation or a steam distillation, the sulfur which is present in theform of soluble sulfur in the crude reaction mixture presents moredifiiculty, and when present during the subsequent acid extraction,interferes greatly therewith because the sulfur precipitates as a blackviscous mass which is difficult to stir and hinders the extraction ofthe 2,2'-dithiobisaniline.

We have discovered that if the crude reaction mix is treated with awater-soluble sulfite that most of the unreacted sulfur can be separatedby conversion to a water-soluble thiosulfate illustrated by Thistreatment may be done after the excess 2 acid extraction and improvesthe yield of the 2,2'-dithiobisaniline.

The residue from the sulfite treatment consists substantially of 2,2'-dithiobisaniline and 4,4- dithiobisaniline. The 2,2'-dithiobisanilineis separated from this residue by extracting with, for example, hotdilute hydrochloric acid, filtering the hot solution and cooling theacid extract to separate 2,2'-dithiobisaniline hydrochloride. The4,4'-dithiobisaniline remains in solution.

The following example is given to illustrate the invention:

Example A solution of 110 grams of sulfur in 204 grams of aniline isheated at 175-180" C. for twenty-four hours. The solution is then cooledand the unreacted aniline removed by steam distillation. The amount ofaniline in the distillate is about grams. The residue is about 205grams.

The amount of unreacted sulfur may be readily calculated if the anilineand sulfur are assumed to react to give aniline disulfides. In thisparticular experiment, 129 grams of aniline are assumed to undergoreaction to aniline disulfides. This reaction will use up all but 43grams of sulfur which will require 172 grams of sodium sulfite forconversion to the thiosulfate.

The crude aniline free reaction product is divided into two equal parts.One half of the material is stirred and heated on the steam bath with aslurry of grams of anhydrous sodium sulfite (a 5% excess over thetheoretical) in cc. of water for six and one quarter hours.

The salt solution forms a layer underneath the oily layer. By theaddition of water the relative positions of the layers can be reversedand the salt solution decanted. The salts are washed from the oil bystirring with two 150 cc. portions of hot water.

The oil is then extracted with 475 cc. hot eight percent hydrochloricacid, the mixture being stirred and heated at 80-90 C. for ten minutes.It is filtered hot. The acid-insoluble residue weighs 3.2 grams and is adark green powder. The corresponding residue from the control is atough, viscous mass weighing 20 to 25 grams.

On cooling the filtrate and scratching the walls of the beaker, thereseparates a voluminous precipitate of light yellow crystals of2,2-dithioblsaniline hydrochloride. This is filtered and dried.

For purification, the hydrochloride is taken up in 200 cc. hot water andthe hot solution decanted from the small amount of oil which is largelysulfur. The free base can be obtained 3 from the warm slurry of thehydrochloride by slow addition with stirring of six normal sodiumhydroxide.

A 30 gram yield of 2,2'-dithiobisaniline, melt- 7 ing from 80 to 88 C.is obtained.

Examples of other'sulfites that may be used are potassium sulfite,ammonium sulfite, and lithium sulfite. 1

It is to be understood that the expression"""" -produced by reaction ofelemental sulfur with alkali-metal herein embraces the. hypotheticalalkali-metal ammonium.

in the crude mix.

The proportiorii'oiii" sulfite used should be-at least 1 molecular.proportion for everymolecular" proportion oi sulfurl reacted sulfur,unreacted aniline, and 2,2-dithiobisaniline is produced, which comprisesremoving unreacted aniline from the crude mixture, then agitating theresulting mix with an aqueous solution of an alkali-metal sulflteforming an oily layer and a watery layerfseparating therefrom the oilylayer containing 2,2'-dithiobisaniline, and extracting from the oilacid-soluble 2,2-

dithiobisaniline with aqueous hydrochloric acid. 3;;5; method ofpurifying 2,2'-dithiobisaniline V aniline, whichcomprises agitating thecrudereful for the invention are exemplified by o-toluia dine,p-toluidine, m-phenylene diamine; toluylene diamine, p-chloraniline,p-xenylamine;

acid-soluble dithio bis-arylamine with. aqueous non-oxidizing mineralacid."-

2. A process of purifying 2,2'-dithiobis-aniline produced by reaction ofaniline with elemental sulfur'wherebya" crudefmixture comprising un- 1;lactionnmixcontaining sulfur and 2,2'-dithiobisaniline with at least onemolecular proportion of 15 sodium sulfiterforevery molecularproportionof sulfur in the crude reaction mixture.

Q i PHILIP T. PAUL.

LYNDON B. TEWKSBURY, JR.

REFERENCES CITED The following'references-are of record the file of:thisz'pa'tent'r" I V UNITED STATES PATENTS" Date 5 Number Name I2,279,277 Shoemaker Apr. 7, 1942 FOREIGN PATENTS Number Country Date 0141,440 Great Britain Apr, 19, 1920 OTHER REFERENGES'I'Q QChemicalAbstracts vol. 2:} (1935),, pages 1790*- Hodgson at page 1140.

ah, J. ChemrSoc (London); 19-34.

